1. Field of the Invention
The present invention relates to an optical receiver module and a manufacturing method for the optical receiver module.
2. Description of the Related Art
There is an optical receiver module for receiving light entered through an optical fiber connected thereto. Such optical receiver module generally includes a lens and a light-receiving element. Light entered through the optical fiber is entered into the light-receiving element via the lens, and the light-receiving element coverts an optical signal corresponding to the light into an electrical signal.
In the conventional optical receiver module, there is a case where the incident light entered into the light-receiving element is reflected by a light-receiving surface, and the reflected light is entered into the optical fiber. Such incident light entered into the optical fiber sometimes causes noise. Generally, in a high-speed and wide-bandwidth optical receiver module for performing high-speed transmission (several Gbits/s or more, for example) of signals, return loss of the light at an incident end is required to be reduced to a predetermined value or less. Specifically, for example, in ITU-T (international standard), the return loss of the light at the incident end is required to be −27 dB or less.
Therefore, conventionally, there has been taken various measures for reducing an amount of the reflected return light that enters into the optical fiber. For example, Japanese Patent Application Laid-open No. 08-186321 discloses a technology for reducing the amount of the reflected return light that enters into the optical fiber by causing a submount to be inclined with respect to an optical axis. Further, Japanese Patent Application Laid-open No. 08-094887, for example, discloses a technology for reducing the amount of the reflected return light that enters into the optical fiber by causing a surface of the submount on which the light-receiving element is mounted so as to be inclined with respect to the optical axis. Further, Japanese Patent Application Laid-open No. 05-152599, for example, discloses a technology for reducing the amount of the reflected return light that enters into the optical fiber by processing the light-receiving surface of the light-receiving element so as to be inclined with respect to the optical axis. Further, there also exists a technology for reducing the amount of the reflected return light that enters into the optical fiber by constituting the optical receiver module, with the optical fiber, the lens, and the light-receiving element being shifted from a central axis of the optical receiver module.